Total $\gamma^*$p cross section

Abstract.

This paper shows that the approach based on Gribov's ideas for photon–proton interaction is able to describe the experimental data over a wide range of photon virtualities $Q^2 = 0$–100 GeV$^2$ and energies $\sqrt{s} = W = 3$–300 GeV. A simple model is suggested which provides a quantitative way of describing the matching between short and long distances (between “soft” and “hard” processes) in photon–proton interaction at high energy. The main results of our analysis are: (i) the values of the separation parameters differentiating the soft and hard interactions are determined; (ii) the additive quark model can be used to calculate the soft contribution to the photon–proton interaction; (iii) a good description of the ratio $\sigma_{\mathrm{L}}/\sigma_{\mathrm{T}}$ is obtained; and (iv) a considerable contribution of the soft process at large $Q^2$, and of hard processes at small $Q^2$ was found